A preferred method in the practice of marine and coastal construction is the assembly of precast (prefabricated) steel reinforced concrete elements. It is also preferable to make the elements floating. The advantages of the floating concrete structures lie in the economy of the materials used (concrete is very well suited to a marine environment), in the fact that it is easy to make concrete structures bouyant for towing in the construction stage, as well as permanently floating, whereas they are heavy enough for a safe permanent installation, and in the fact that they can also provide storage space. Concrete structures may be constructed in a convenient, protected area then floated to the installation site. This method is used with advantage to avoid the occupation of expensive land for production site. Even if the installation site is highly exposed to the weather, the structure can be quickly positioned during a short window of favorable conditions.
The range of applications of floating and non-floating concrete structures is fairly large:                Oil exploration, drilling and production platforms, LPG terminals;        Barges, ships and yachts, floating docks;        Floating, or based on the ocean floor, artificial islands, airports, power stations, industrial plants, hotels, shopping centers, bridges, semi-submersible tunnels, lighthouses, breakwaters, etc.        
Large structures can be assembled from precast components integrated by cast-in-place joints or by match-cast joints. A combined application of precast and cast-in-place elements is also possible. Precasting allows thin sections of high-strength concrete to be obtained.
An additional advantage is obtained by making the precast components modular, i.e. when structures are assembled from a plurality of large, essentially identical modules. Thus, JP 01127710 discloses a method for construction of a marine structure such as a platform or an artificial island, from hollow modules with rounded bottoms, about 10 m in diameter and 5 m deep. The modules may be shaped as rectangular or hexagonal boxes, or as cylinders. They are positioned by floating and are assembled in one or two directions in horizontal plane, in large floating groups that may be then towed and connected in a large marine structure.
JP 02120418 discloses a method for construction of foundations for marine structures from large hollow T-shaped blocks. The blocks have dovetail vertical channels at the connection sides and vertical wells for piles. The blocks are towed to the construction site and sunk in place. Adjacent elements are connected by steel or ferroconcrete profiles inserted in the dovetail channels, and bearing piles are driven into the sea bottom through the vertical wells. Joints are formed in the dovetail channels by injecting mortar or grout.
U.S. Pat. No. 3,799,093 discloses a pre-stressed floating concrete module for assembling wharves. The module is of rectangular box-like shape and has a core of buoyant material, pretensioned strands of steel along the edges of the box, and brackets for joining to adjacent modules in one line.
U.S. Pat. No. 5,107,785, describes a similar concrete floatation module for use in floating docks, breakwaters and the like. The box-shaped module has integral tubular liners embedded along one set of its parallel edges. Tensioning steel cables are passed through the tubular liners to maintain a line of several modules in compression in an end-to-end relation. Similar tubular liners may be provided in the transverse direction to interconnect several lines of modules. Yet another similar floating concrete module is disclosed in U.S. Pat. No. 6,199,502 where the module has also box-like shape but with slightly concave abutting sides to ensure more stable mutual positioning of the adjacent modules. There are provided passages for two transverse sets of connecting cables in each module, in two horizontal planes displaced from each other.